How to determin IT requirements

I would like to know where I can find information on how to go about setting up IT services for a small company and what is invloved. Questions to ask in determining what we need and what is overkill. I work for a Life Safety company of 30 employees, 2 Admin, 2 Managers, 1 Acountant, CEO, and 24 people in the field. We would like to set up a web / email server and provide the field employees with notebook computers to be able to access blueprints, specs, and forms.

Thank you,
Lance